Difference between hardwired control unit and micro-programmed control unit

 

Hardwired control unit

 

1. It uses flags,decoder,logic  gates and other digital circuits.

                                 Block diagram

2. As name implies it is a hardware control unit.

3. On the basis of input Signal output is generated.

4. Difficult to design,test and implement.

6. Inflexible to modify.

7. Faster mode of operation.

8. Expensive and high error.

9. Used in RISC processor.

Micro-programmed  Control Unit

1. It uses sequence of micro-instruction in micro programming language.

2. It is mid-way between Hardware and Software.

3.It generates a set of control signal on the basis of control line.

4. Easy to design,test and implement.

5. Flexible to modify.

6. Slower mode of operation.

7. Cheaper and less error.

8. Used in CISC processor.

Advantages and disadvantages of hardwired and micro-programmed control unit.

 

Advantages of micro-programmed control unit

    1. Simplifies design of CU.

    2. Cheaper

    3. Less error prone to implement.

Disadvantage of micro-programmed control unit

    1. Slower compared to hardwired control unit.

Advantages of hardwired control unit

    1. Faster than micro- programmed control unit.

    2. Can be optimized to produce fast mode of operation. 

Disadvantages of hardwired control

    1. Instruction set control logic are directly 

    2. Require change in wiring if designed has to be controlled.